/Engine/Plugins/Online/OnlineServices/Source/OnlineServicesCommon/Public/Online/SessionsCommon.h
This event will trigger as a result of joining a session.
virtual [TOnlineEvent](API\Plugins\OnlineServicesInterface\Online\TOnlineEvent)< void(const [FSessionJoined](API\Plugins\OnlineServicesInterface\Online\FSessionJoined) &)> OnSessionJoined()